Method and system for handover in cellular wireless using route programming and training processes

ABSTRACT

A method and system for managing handover where a database that receives location information about a moving object includes information regarding which base station is used in a current radio link connection and which base stations were used from historic radio link connections. Using the base station radio link history of the object and an electronic map, a processor coupled to the memory of the database selects which physical path the moving object is using. Upon matching the object&#39;s path with a history of path routes on the list, the processor will apply an optimized handoff sequence to the moving object. The optimized route can be derived from an algorithm that processes previous historical data from moving objects traveling on the same route. Methods of providing the location of moving objects via location sensors may be used to provide the database with higher resolution information about a moving object&#39;s location on an electronic map and allow further enhancement of the handoff optimization. Generally, location data is used to quickly determine which route the moving object is using and more quickly assign an optimized handoff sequence. Historical data along known routes can include time and spatial information to be processed by the routing algorithm. The database may reside in a central location or within each moving object or a combination of both.

FIELD OF THE INVENTION

The present invention relates generally to managing radio link handoverin a cellular wireless environment. More particularly, the presentinvention relates to a method and system for selecting optimum basestations for operating range and data throughput within any small cellwireless system.

BACKGROUND OF THE INVENTION

Within cellular networks, handover of a mobile station from one basestation to the next occurs via either soft handoff or hard handoff.

An individual base station has finite reach and finite bandwidth thatresult in deployment of multiple physically or directionally separatedbase stations to serve large areas or where there are high counts ofactive mobile stations. Multiple base station signals covering a commonphysical point may be separated into wireless cells by frequency band,time slots, spreading codes, spatial selectivity, or combinations ofthese four techniques.

When an active mobile station with a single radio moves from one cell toanother, the mobile station has to switch between cells while it iswithin the region where the two cells both have coverage. This is donein order to minimize gaps in communication. With current technologies,either the mobile station will initiate the cell association transitionwhen communications begin to fail on the existing link, or the mobilestation will be commanded by the cellular network to change at what itbelieves is the appropriate time to the next frequency, timeslot,spreading code, or spatial selection in order to communicate with thenew targeted cell.

Depending on the radio technology selected, the mobile station may onlybe able to communicate to just one cell at a time. In that case theprevious cell connection must be dropped before the connection is madeto the new cell. These types of cell-to-cell changes are termed a hardhandoff, so called because once the handover is started there is nogoing back—i.e., there is no “soft time” when the radio client iscommunicating to more than one cell where the system could decide tomove back and forth several times between the cells.

Where the mobile station is managing the changeover, it can takeconsiderable time (i.e., several seconds), especially in a crowded radiofrequency (RF) band, to search for the next best cell with which tocommunicate. There are also smaller delays associated with negotiatingwith the next cell for communication rights. During this time, if thesystem is only capable of hard handoffs, communications are lost If themobile station has the ability to communicate with more than one cell ata time an alternative handover technique can be used where beforecommunications are dropped to the old cell, communications are initiatedand setup completed to the new cell.

Soft handoffs are typically used on large cellular networks with cellscovering many kilometers, the delay associated with searching for thenext best cell is largely eliminated by having a central controllerdetermine when is the optimum time and which cell is next to be usedwhile the mobile client is still communicating on the old cell. The timeto change cells is determined by measuring the wireless loss between themobile client and all cell towers that detect the mobile stationssignals. The relatively slow fading of the signals in such a systemallows sufficiently accurate predictions as to when the mobile stationwill reach the effective edge of the existing and new cells. Althoughrough location of mobile clients is determined by the same mechanisms,the algorithms are power and time trend based rather than locationbased.

An example of a technology where soft handover can be done without goingto the expense of having a completely duplicated radio section is CodeDivision Multiple Access (CDMA) where the signals from more than onecell can be separated from within in single frequency receive band. Themobile station has a single RF receiver that converts radio frequencydown to baseband, but assigns a specific spreading and despreading codeto each user. These codes allow the required signals to be separatedfrom other signals by correlation.

In addition to the use of spreading and de-spreading codes commonly a“rake receiver” with multiple narrow band filters (fingers) is used.This allows strong interference signals to be eliminated but also allowsmore than one adjacent cell to operate on the same frequency if eachcell base-stations rake settings are coordinated to be different toadjacent cells. The single RF receiver picks up all of those that arewithin range allowing communication to more than one cell at a time

Commonly, when the active mobile station is about halfway between twobase stations, the mobile station handles transport of data back andforth to the cell along with actively looking for other cells. When themobile station finds a base station with sufficient signal strength, themobile station informs the network accordingly. The network might decideat that point to route the call through both base stationssimultaneously such that the handoff process happens in multiple stepswhen the active mobile moves from one cell to another. First the mobilestation notices a receiving base station, which then begins to carry thecall in addition to the originating base station. As the mobile stationcontinues to move, eventually the signal strength from the originatingbase station will drop to the point where it is no longer useful. Again,the mobile station will inform the network of this fact and theoriginating base station will be dropped in a soft transition. Thus,such a transition is termed soft handoff.

Typical soft handover systems require a centralized handoff controlsystem with extensive knowledge and control of all base stations. Thisis not always practical especially when working within a large number oflow cost standalone base-stations are used. Some current technologieswhich normally do not include a centralized handover mechanism areWiMAX, WiFi, WirelessMAN™, ZigBee™. WiFi® is a short range low cost besteffort wireless data networking standard based on IEEE Standard 802.11.Typical WiFi® data rates are around 3Mb/s but in excess of 100Mb/s istargeted. ZigBee™ is a wireless networking standard based on IEEEStandard 802.15.4 that is aimed at remote control and sensorapplications and is suitable for operation in harsh radio environments.WiMAX and WirelessMAN™ protocols are currently defined through IEEEStandard 802.16 where a wireless metro area network (MAN) providesnetwork access to buildings through exterior antennas communicating withcentral radio base stations. The wireless MAN offers an alternative tocabled access networks, such as fiber optic links, coaxial systems usingcable modems, and digital subscriber line (DSL) links.

Conventional handover techniques over time, allow more radio inter-celltransfers to occur than necessary and that reduces overall networkefficiency. Further, conventional wireless networks utilize a largenumber of base station radio links where momentary radio links can causedisruptions to both data throughput and management of data flow throughthe network.

Loss of signal in many small cell applications can be of significantconsequence. For example, real-time video feed from a mobile wirelessvideo camera for surveillance applications can require significantamount of memory buffering and consequent latency in order to be able toprevent such loss of signal resulting in data corruptions. It wouldtherefore be desirable to provide a mobile station handover in a smallcell environment in a more predictable manner similar to soft handoff toalleviate fading problems, resultant signal degradation, orcommunications failure in terms of, but not limited to, complete loss ofsignal.

When cells become much smaller i.e. have individual cell coverage areasunder a km in diameter (micro-cell), or even just a few meters indiameter (pico-cells), the radio transmissions when exposed to thetypical multiplicity of dynamic elements which reflect and shadowsignificant amounts of RF power, the location of the usability edge ofcells becomes very much more difficult to determine by conventionalsignal power loss techniques. In such cases, signals may fade to nothingin a fraction of a second or over just a couple of meters. Especiallywith micro-cell and pico-cell systems, knowing exactly where to initiatehandoffs becomes critical and requires a more accurate mechanism than iscurrently available in large cellular systems. This applies to bothsystems with hard handoffs and systems with soft handoffs.

SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at leastone disadvantage of previous handover techniques especially within smallcell networks. The present invention provides improved handover that canbe used where a mobile station is traveling closely to a known path atlimited speeds. Moreover, the present invention involves generating andusing an electronic map indicative of switching points for optimizedhandover.

It is, therefore, desirable to provide a method of managing handoverwithin a radio cellular environment, the method including: determiningan identification of a mobile station that is known to normally follow apredetermined route corresponding to the identification; comparing theidentification with a database having stored maps of known routesegments including a list of base stations along each of the known routesegments; and assigning a preferred sequence of base stationscorresponding to one or more of the known route segments along thepredetermined route.

In a another aspect, the present invention provides a method ofoptimizing a managed handover technique within a radio cellularenvironment, the method including: determining an identification of amobile station traveling along a path, the mobile station having noprevious history of base station connectivity; as the mobile stationestablishes a connection with a base station, associating, based uponthe base station being used by the mobile station, the identificationwith a known route selected from a database having stored maps of morethan one the known route including a list of base stations along eachthe known route; as the mobile station disconnects from the base stationand connects to a subsequent base station, storing historicalinformation regarding the base station and the subsequent base station;comparing the base station and the subsequent base station to the listof base stations along the known route in order to identify one or moreof the known routes that include both the base station and thesubsequent base station; repeating the storing and comparing steps forfurther subsequent base stations, until only one of the known routesremains and corresponds to the path traveled by the mobile station;determining whether a direction of travel of the mobile station alongthe path is forward or reverse along the known route that corresponds tothe path; identifying one of the stored maps from the database thatcorrelates to both the direction of travel and the known route remainingthat corresponds to the path traveled; and assigning a preferredsequence of base stations corresponding to the one of the stored mapsfor all further connections with the mobile station along the path.

In a further aspect of the present invention, there is provided a systemfor managing handover in a radio cellular environment, the systemincluding: a centralized communications center having a basetransceiver, a central server, and a database; a mobile station havingone or more transceivers capable of communication with the centralizedcommunications center via one or more base stations, the mobile stationbeing assigned a preferred sequence of the one or more base stationscorresponding to one or more known route segments along a predeterminedroute followed by the mobile station.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached figures.

FIG. 1 is a simplified schematic of a small cell radio environmenthaving a mobile subscriber station (MSS) situated within a simplifiedillustration of a bus in accordance with one example of the presentinvention.

FIG. 2 is a simplified schematic of a downtown core with buildings andmultiple base stations in accordance with another example of the presentinvention.

FIG. 3 is a simplified schematic shown in block diagram formrepresenting the MSS such as in FIG. 1 in accordance with one example ofthe present invention.

FIG. 4 is a basic system network diagram in accordance with the presentinvention.

FIG. 5 is schematic showing the wireless micro-cell handover controldetails from a different level than FIG. 4 in accordance with thepresent invention.

FIG. 6 is a basic configuration showing handover with centralizedmapping of one or more shared databases in accordance with the presentinvention.

FIG. 7 shows a micro-cellular network covering a highway with exemplarycell switching locations overlaid in accordance with the presentinvention.

FIG. 8 is a block diagram exemplifying the information control loops inaccordance with the present invention.

FIG. 9 is a relatively detailed diagram of one embodiment of themanagement system in accordance with the present invention with on-boardroute optimization.

FIG. 10 is a relatively detailed diagram of another embodiment of themanagement system in accordance with the present invention withcentralized route optimization.

FIG. 11 is a relatively detailed diagram of yet another embodiment of amore centralized management system in accordance with the presentinvention with centralized route optimization.

DETAILED DESCRIPTION

Generally, the present invention provides a method and system formanaging radio link setup and disconnect between base stations andsubscriber stations. The present invention alleviates disadvantages ofespecially small cell wireless protocol that do not have handoverprotocol. The present invention avoids use of conventional handovertechniques so as to prevent excessive radio links from occurring. Thepresent invention is useful, among other applications that will becomeapparent to one of ordinary skill in the art of networking, inapplications where the subscriber station (e.g., mobile station) followsa known route that has a series of base stations along and beside thesame route. The present invention includes methods for selecting theoptimum base stations for best operating range and data throughput.Ideally, the present invention assists in reducing control traffic assuch control traffic often reduces actual payload capacity. The presentinvention also minimizes or substantially eliminates association time toperform handover that, for example in IEEE 802.16(d), can be around 15seconds. The present invention also substantially eliminates short-termconnections in the network and optimizes data throughput to each mobilestation.

Broadband wireless in small cell protocol settings (e.g., 802.16)includes a variety of applications. However, for purposes of clarity,the illustrative embodiment discussed herein will be drawn to thesecurity application of real-time video on city busses within a downtowncore. Such security video application is a high bandwidth systemtransmitting in real time over a wireless system where fading rates mustbe kept low for real time dependable video links. Learning, ordeducting, the preferred routes in order to predict fading and use themost appropriate choice of base station is a desired goal of the presentinvention, as is minimizing the number of base station radio links used.This increases overall efficiency, radio resource usage, and preventsloss of links. Specifically, momentary radio links cause disruptions todata throughput and management of data flow through the network. Thepresent invention allows the use of radio protocol standards that do nothave handover protocol as part of the standard. While such specificimplementation is discussed in terms disruptions to a video securityapplication on city busses, it should be readily apparent that thepresent invention is intended for any other application operating withinan environment with rapid and unpredictable fading and should not beconsidered limited to a bus security application.

With regard to FIG. 1, a simplified schematic of a radio cellularenvironment 100 is shown having a mobile subscriber station (MSS) 121situated within a simplified illustration of a bus 120. The MSS 121 maybe any suitable radio transceiver with one or more antenna. The antennamay be directional such that if two antennae are used, they may bedirected in opposite directions. The MSS 121 itself may be mounted atopand external to the bus 120. Alternatively, the antenna(e) operating inconjunction with the MSS 121 may be external to the bus, while theprocessing circuitry of the MSS may be located separate from andinternally within the bus 120. Further, the MSS 121 may include morethan one radio transceiver such that one may be dedicated for radio linkmanagement and another may be dedicated for data transfer. Suchimplementation details regarding the MSS 121 specifics will not bedescribed further as such would be considered well within the knowledgeof one of ordinary skill in the art of radio transceivers.

The MSS 121 operates in communication with sensor mechanism such as, butnot limited to, a video camera 122. As appropriate to the securityapplication of the present invention, the video camera 122 is discreetlylocated for viewing occupants of the bus 120. It should be understoodthat more than one security camera may be used within the bus and may beco-located with any other type of sensor mechanism including, but notlimited to, noxious gas detectors, infrared heat sensors, or any devicecapable of detected a security-related characteristic within or near thebus 120. For purposes of clarity, such devices are not further describedherein. The video camera 122, or any related device, is coupled to theMSS 121 by any means that provides a high data transfer capability. Thismay include hard wiring or wireless communication transmitter within thevideo camera 122, or device, via a low range wireless protocol.

As the bus 120 travels along its route, the MSS 121 also moves alongsuch known route. Base stations 130, 140, and 150 are located within theradio cellular environment 100 along the possible bus routes illustratedgenerally by streets 170. A centralized communications center 110 existswithin the radio cellular environment 100. The centralizedcommunications center 110 may function within a closed network or may beconnected to the Internet, public switched telephone network (PSTN),local area network (LAN), wide area network (WAN), metro area network(WAN), or any one or combination of networks. The centralizedcommunications center 110 includes at least a base transceiver 111, acentral server 112 with appropriate processing capability, and adatabase 113 for storage of route information. The base transceiver 111is in wireless communication, via a small cell protocol as discussedhereinabove, with base stations 130, 140, 150. It should be understoodthat a variety of configurations may exist in an actual physical settingin a cityscape, but for purposes of clarity only three base stations anda single T-intersection are shown in FIG. 1.

With reference to the simplified radio cellular environment 100 shown inFIG. 1, the innovative operation of the present invention involvesmanaged handover of the MSS 121 from one base station to another whilethe bus 120 travels along streets 170. Radio links 160, 161, 162, and163 are shown and illustrate the fact that, at certain points of travel,the MSS 121 is capable of communication with more than one base station.In this instance, base station 130 is connected to the MSS 121. Further,base stations 140 and 150 are active, though not connected to the MSS121. As shown, the MSS 121 is in communication with the central basetransceiver 111 via radio links 160 and 161 as the active connection isvia base station 130. When the bus 120 enters the intersection, basestation 140 will attempt a handshake with the MSS 121 via radio link162. Due to the proximity of base station 150 when the bus 120 entersthe intersection, the base station 150 will also will attempt ahandshake with the MSS 121 via radio link 163.

In terms of the radio cellular environment 100 as a whole, the resourcesrelated to radio links 162 and 163 can be considered duplicative anddisruptive. This is readily apparent if one considers the path of thebus 120. If the bus were to travel in the direction from base station130 to base station 150, there would be no need for any use of radiolink 162 because handover would ideally occur from radio link 161 toradio link 163. Alternatively, if the bus were to make a right turn andthen travel in the direction from base station 130 to base station 140,there would be no need for any use of radio link 163 because handoverwould ideally occur from radio link 161 to radio link 162. In actuality,the path of the bus 120 is normally a known route. For example, anEast-bound #1 bus may take the known route from base station 130 to basestation 150, while a South-bound #2 bus may take the known route frombase station 130 to base station 140. The #1 bus would therefore have acertain predetermined and known route uniquely tied to its identifier(i.e., #1), while the #2 bus would therefore have a different certainpredetermined and known route uniquely tied to its identifier (i.e.,#2).

In accordance with the present invention, the known routes arecorrelated to the sequential list of base stations to be used during thetravel of the bus 120 through its corresponding route. As should beapparent from FIG. 1, different known routes will result in differentsequences of base stations. Still further, it should be understood thatthe sequential list of base stations used might not always reflect basestations with the strongest signal relative to the given position of theMSS 121 along the path of travel. Rather, each base station is selectedbased upon the actual known route traveled. This may require that somevery strong base station links should be ignored, while weaker links maybe sought. In terms of the FIG. 1, if the bus 121 were traveling in aknown route from base station 130 to base station 150, then radio link162 should be ignored upon handover from base station 130 to basestation 150 even if radio link 163 is stronger than radio link 162. Ifradio link 162 were to handover to connection of the MSS 121 to basestation 140, even momentarily, this would inefficiently use radioresources as link setup and teardown between the central transceiver 111and base station 140 would occur.

Because the bus 120 passes the T-intersection rather momentarily, even atemporary loss of signal could be tolerated given the predictability ofthe known route and the impending link setup with radio link 163 as thebus travels towards base station 150. In such instances of such atemporary loss of signal, it would be well within the intended scope ofthe present invention to provide a memory buffer on-board the bus 120integrated or otherwise coupled with the sensing device (i.e., videorecorder 122) and/or the MSS 121. Such on-board memory buffer would alsobe part of on-board memory as a whole that would provide storage of thesequential list of base stations. Further, the on-board memory may becapable of storage of one or more of the sequential lists of basestations depending upon the preferred route used by any given bus. Inthis way, a single bus may be used for any one of several known routeswhere the sequential list of base stations may be selected given theroute identifier.

In further accordance with the present invention, a collection of allknown routes and the related sequential lists of preferred base stationscan be centrally stored at the central communications center 110 withina database 113. Such stored known routes may be in the form of routemaps, look-up tables, or any suitable storage format. The known routesmay also be broken into smaller segments, or steps, that wouldcorrespond to unalterable sections of any given known route. In thismanner, centralized computing intelligence at the central server 112 canbuild a map from known route segments and provide such map to the MSS121 such that the MSS 121 follows a sequential list of preferred basestations by way of a managed handover along a chain of each base stationin the list. It is well within the intended scope of the presentinvention to provide the central server 112 with the computingintelligence to recombine known route segments to build maps that mayvary according to the path of the bus. Building such varying maps may bedone in several ways including, but no limited to, real-timereassessment of the bus' geographical location, speed, direction, ortime-of-day, or exigent circumstances, or any other similar variablethat may require route deviations on-the-fly.

The computing intelligence would preferably be located at the centralserver in order to reduce the amount of control data sourcing from theMSS 121. However, some level of computing intelligence may existon-board the bus 120 such that one or more known route segments may beutilized to if the bus were to deviate from the known path associatedwith its identifier at a time when loss of signal to the centraltransceiver 111 occurs. Such occurrences could of course be the resultof an unexpected or unwanted deviation of the bus 120 from its path. Insuch instances, maintaining the radio link and related transfer of videoand/or any other sensed data would be a priority.

In operation, the method in accordance with the present inventionincludes handover along a route to provide wireless access along theroute. FIG. 2 shows a simplified schematic of a downtown core withbuildings 210 and five base stations BS1 through BS5 though more or lessbase stations may be involved. As well, the buildings 210 may of coursebe of varied shapes and sizes such that streets therebetween may varyfrom the simplified grid pattern as shown in FIG. 2. For purposes ofillustration as well, it is assumed that the buildings 210 areinfinitely tall such that radio links 200 from with the base stationsare narrowly formed in terms of their effective beams. This is thereforerepresentative of the fact that a downtown radio environment among tallbuildings is a limited radio environment that can include constrainedradio beams with related signal voids and fading problems. The location,and hence availability, of each base station BS1 through BS5 areprogrammed into the central server 112 (shown in FIG. 1) that isaccessible by the MSS and base station. Each MSS and base station has anidentifier (ID), MSS-ID and BS-ID, respectively. The MSS-IDs and BS-IDsand the use of training sequences or preprogramming enable the creationof stored maps or lookup tables used to establish optimum links.

As the bus 120 moves and the corresponding MSS traverses along the knownroute applicable to the given MSS, the MSS will look for the next BS-IDin the known route sequence. Once the next BS-ID is found, the MSSestablishes a new radio link with that BS and will ignore any otherradio links. In terms of FIG. 2, this would mean that the BS-ID of BS2would be ignored when the bus 120 travels the known route from BS3 toBS5. It is important to note that any other radio links are thereforeignored regardless of the fact that they may have sufficient radiosignal strength. Such other radio links are ignored because they do nothave the expected BS-ID. This is a useful aspect in regards toenvironments such as a downtown core with multiple radio linksinterspersed among a canyon of tall buildings.

As mentioned, each MSS follows a known route where the known route canbe considered a series of repetitive steps within an environment ofmultiple radio links. Each step may be represented by traveling acertain distance in a certain direction for a certain period of time ata given rate of travel. When two or more such steps are repeated inseries, they therefore from a predictable route. While such routes mayin fact deviate slightly due to traffic, construction, or some otherobstacle or situation, only a portion of the route would use a differingstep from the known route. Such a detour along the route could bepermanent, temporary, or varied in term. Deviation from the known routemay of course be related to a host of variables including, but notlimited to, time of day, weather conditions, or emergency situations.

Each known route and its constituent series of steps must initially bedetermined in accordance with the present invention. A training processwould therefore be utilized within the present invention. During thetraining process, one or more MSS follow a repetitive route that has aseries of base stations along and beside the route. Each MSS identifiesthe optimum base stations to use that provide best reach and datathroughput. It should be noted that best reach and data throughput maynot mean that the base station with the strongest signal is identified.Rather, identifying the most appropriate base station for any given MSSshould also consider the path taken by the MSS.

For example, turning a corner may enable an MSS to identify a weakerbase station and a stronger base station. However, due to the directionof travel of the MSS, the weaker base station may strengthen as the MSStravels towards it. Likewise, the stronger base station may then fade asthe MSS. travels away from it. This would result in the preferred basestation for handover receipt actually being the base station that wasweaker at the time of turning the corner. The inventive training processwould identify all such situations and effectively create a map of whichbase station to use along any given route. The map may be a stored listof a series of base stations. Each map may have slightly differingversions that allow for the possible deviations mentioned above alongany given known route. Still further, each map may be reversible suchthat a route can be traveled in reverse with the knowledge of theappropriate series of base stations. Such reversible maps would beuseful in terms of inbound and outbound busses traveling along theidentical streets.

The training process therefore produces maps of each known routetraversed by the MSS that identifies each appropriate base station touse to ensure robust operation of broadband service between the MSS andthe network. Because each MSS may likely only travel one particular pathwith some possible list of deviations, only a small group of known pathsand related stored maps are needed for any given MSS. In terms of abussing schedule, a downtown express with an 8:15 AM start time and 9:30AM finish time may only require, for example, five or six possiblepaths. Each path would be determined by a training process to form thefive or six known routes stored as maps. Each of the five or six mapswould preferable be stored onboard the MSS. Because the same bus may beused for other routes, the onboard storage of the MSS would therefore berewritable such that each MSS is programmable. Collectively, multiplemaps for many different known routes and their respective deviationswould exist. The collective maps would reside on a central server.

During the training process, the MSS would write the data forming a mapto a central server for central storage. Training on a different routewould therefore collectively add to the data to form the collective mapscentrally stored on the central server. Once all routes are mapped andstored, the training process becomes a lesser function of the presentinvention. Only situations where new routes due to, for example,revisions to demographic changes or expansion to city infrastructure andrelated revised bus schedules would require a new training process tooccur. Once all known routes and deviations are mapped and stored withregard to the appropriate base station sequences, the present inventionwould manage handover throughout the entire network in a predictable andefficient manner. Fading and related loss of signal could therefore becontrolled and minimized. This is due to the information regarding themost appropriate link handovers being passed to the network to enabledata throughput optimization when there are more than one MSS linked toa base station or more than one base station linked to an MSS.

It is also an important feature of the present invention that any MSScan obtain a priority bandwidth for emergency services. This can beaccomplished by using the centrally stored map information for the knownroutes and their constituent segments, or steps. For example, a bus(i.e., MSS) may significantly deviate from its typical known routeespecially during an emergency. In such instance, the MSS will request apriority bandwidth. The priority bandwidth may require identification ofa new map including a base station sequence that deviates from anypreviously mapped and stored known route. The new map may beinstantiated based upon the MSS location, path, speed, or other relevantinformation alone or in combination, and formed from the various knownsteps within each known route. This would require processingintelligence at the central server in conjunction with a locationdetection means.

The processing intelligence could be in the form of a central processingunit (CPU). The location detection means may be in the form of a globalpositioning system (GPS) device; in-road sensor element such as, but notlimited to, buried resonance coils; wheel rotation measurement devices;triangulation computing devices; or any similar mechanism or combinationof mechanisms that can sense the location, path, and route of the MSSand convey such information to the processing intelligence. Further, thelocation detection means may be also be of the type disclosed withinU.S. Pat. No. 6,965,827 issued to Wolfson, herein incorporated byreference.

The training process of the present invention may be an adaptivetraining with or without GPS. The initial bus trip training includesswitching to discovered base stations with the strongest signal as andwhen fading requires a change. In addition radio link parametrics arestored in the central database (element 113 in FIG. 1) containing knownradio paths, duration of links, and whether operational locationinformation (GPS or a similar location detection means) is available. Afirst pass through a route by the MSS defines the approximate potentialend points of each link's capabilities. On the second pass over the sameroute, the training algorithm attempts to link to the furthest basestation along in the previous link sequence. This gives the approximatepotential start points of each link. On subsequent passes and duringnormal operation, the links to be used are selected based on acombination of the average historical duration of the radio link andeffective radio link throughput. In particular, where the link durationis small compared to acquisition times, it may be determined that toswitch to a particular link although strong is not appropriate. On eachsubsequent trip link, range and performance are determined and averagedinto the database 113. Where the radio system environment 100 hasmulti-channel capabilities, the inactive channel is used to search foralternative links. If an expected radio link is missing on a trip thenext best base station can be used. The database 113 can also be used toanalyze base station deployment location improvements and resiliency tofailure.

Alternatively, a flexible route operation with GPS is possible. In aflexible route operation, an optimum radio link for any given MSS can bemodified for varying routes as long as each section (i.e., segment) ofthe route taken has been mapped by a previous bus route. When a pathchange is detected the database is searched for an optimum path to radiolink mapping for that route subsection (i.e., route segment).Modification of selected links in terms of the preferred sequence ofbase stations can occur due to knowledge of proximity of other buses.Moreover, the inventive methodology can be further modified to includeallowing for base station loading from other MSSs. With reference toFIG. 3, a schematic is shown in block diagram form representing the MSS121. As mentioned above, the MSS 121 may include one or moretransceivers that may be oppositely directed (i.e., forward/backward interms of bus direction).

As shown, transceiver 310 and 320 are connected to a controller 330. Thetransceivers 310 and 320 may function under any radio cellular protocoloperating within the radio cellular environment of the presentinvention. The controller 330 may include a multiplexer for Internetprotocol (IP) packet routing along with a multimedia communicationsserver (MCS) and/or IP-Based multimedia subsystem (IMS) for policycontrol, session control, and quality of service (QoS) control. Aspreviously described, the MSS 121 may involve some level of on-boardintelligence 350 that may be in the form of a database and CPU. Theon-board intelligence 350 could store known route maps and/or segmentsfor any given known route or portions of known routes related to thegiven MSS-ID assigned to the MSS 121 where differing bus routes wouldequate to differing MSS-IDs. Further, a location detection means 350 isalso shown connected to the controller 330. Preferably, the locationdetection means 350 is a GPS device and is therefore shown with relatedradio link.

The processing intelligence in accordance with the present invention mayalso provide for bandwidth and channel allocation to each MSS based onoverall network load sharing to optimize performance. In such instance,the information obtained by the location detection means along with thestored maps regarding the known routes can be used to manage loadsharing. Moreover, it should be understood that the processingintelligence in combination with the location detection means can beused in either the initial training processes for each MSS route or inupdating or augmenting the centrally stored maps via further training.It is also within the intended scope of the present invention to providea training process that can augment the centrally stored maps in such amanner so as to eliminate or change a base station from any given routewhere that base station causes a reduction in data throughput to thenetwork (i.e., bus community).

As mentioned above, GPS may be utilized to locate the bus in itslocation along. The location and relative movement of the bus cantherefore be determined with information using GPS or AGPS if the MSSincorporated an AGPS-capable cell phone or was otherwise AGPS-capable.FIG. 4 shows a basic system network diagram in some detail utilizing aGPS satellite network via either an AGPS cell phone or GPS device.Either location mechanism would locate the bus and communicate with acentral server to determine one or more possible future links to the busbased upon knowledge of the current active link, bus location, andrelated expected routes. Various locations along any given route can bedesignated as trigger points, or switching points, that would indicatethe specific location of a bus where handover will be predetermined tooccur. The maps stored at the central server already mentioned abovewould effectively form electronic maps of suitable switching points. Anychange in the wireless link would be based upon a trigger pointcalculator based upon the expected routes for one or more busses at thatlocation. Though the electronic maps of suitable switching points wouldnormally reside at the central server, it should be understood that suchmaps may be downloadable to the MSS on the bus in any part or wholenecessary to effect optimal handover on any given route.

FIG. 5 is schematic showing the present invention from a different levelthan FIG. 4 and includes wireless micro-cell handover control network. Ahoneycomb pattern illustrates a typical cell arrangement of receptionzones with a possible bus route therethrough. Micro-cellular radio basestations are also shown represented by lampposts on which such basestations are commonly mounted. Multiple cameras may also exist at one ormore lamppost. The cameras and/or base stations may be linked in somewireless or fixed (e.g., optical fiber) manner to a packet network. Thepacket network may communicate the Internet as a while via a wirelesslink to a cell tower shown, for example, as a third generation (3G)WiMAX tower. The central management processor for handover control isshown to reside in the packet network. Communications between the basestations and the central management processor are therefore based onpacket switching.

FIG. 6 is a simplified linear view similar to FIGS. 1 and 2 and shows abasic configuration of handover in accordance with the present inventionwith centralized mapping. As a bus moves along a bus route, the bus willencounter a series of base stations 34, 35, 36, that form a radiointerface between the bus and the packet network. The packet network inturn communicates with a centralized mapping system. The centralizedmapping system may include a mapping mechanism 64 with processingintelligence in terms of a CPU 70 and one or more databases ofelectronic maps of switching points in terms of database 62. Further, asystem management interface for monitoring handover may be provided interms of some graphic user interface 66 and data input mechanism 68 tofacilitate central control of the invention by a system operator. As thebus moves along the bus route, it should be readily apparent thatcommunications between the bus and the central mapping system willmigrate from radio interface A to radio interface B to radio interfaceC. The central mapping system ensures that switching points are adheredto in accordance with the electronic maps stored in the database 62 suchthat precise handover occurs at the optimum location for the givenroute.

FIG. 7 gives an exemplary view of how RF cell switching locations relateto a route map. Three cell coverage areas are shown on the visiblesection of a highway. By analyzing the effectiveness of connecting tovarious cells the system has determined by a the combination ofcalculations and iteration described in this patent where the optimumlocations are that should trigger a cell handover. For a given handoverregion a single RF cell switching location could be used for bothdirections of traffic on the route but alternatively as shown therecould be additional locations for each direction of traffic and also forother variations such as which lane the vehicle is believed to betraveling along and vehicle type.

When used with radio systems capable of a soft handover a secondary setof adaptively determined absolute or relative locations may be definedto allow the separation of when negotiations with the new cell arecommenced and when actual data flows should be transferred to the newcell. This allows initial negotiations to start closer to the edge ofthe new cell where signal to noise ratios are not sufficient to achievethe desired data rates but are sufficient for the negotiation process.Alternatively a soft handover could be commenced from a single set oflocations and the data transfer time determined by a combination of oneor more methods such as the completion of negotiations with the newcell, a predetermined time delay or a speed of travel related timedelay.

In order for the present inventive method and system to function,several loops should exist in terms of information control. FIG. 8 is ablock diagram exemplifying the desired information control loops inaccordance with the present invention between the bus driver and thesystem operator—i.e., system operations, administration, and management(OA&M). An information control loop will of course exist between the busdriver and the system operator. This may include input/output (I/O)information such as passenger statistics and other data provided by thebus driver to the systems operator and specific route or administrativeinformation from the systems operator to the bus driver. A series ofinformation control loops may also exist between an on-board bus controlsystem and the central control system where each such loop may utilizeone or more element such as, but not limited to, GPS satellites, APGSsubsystems, wireless network systems, and transit detectors (e.g.,buried resonant coils). Each such element has been already describedhereinabove.

Additionally, an information control loop may directly exist (e.g., on adirect control channel) for direct data exchange between the on-boardcontrol system and the central control system. The direct controlchannel may exist by a separate radio within or in conjunction with theMSS on the bus. Direct human intervention may also be required from timeto time such that information control loops should exist between the busdriver and the on-board control system and as between the systemoperator and the central control system. Implementation of all suchinformation control loops is well within the understanding of one versedin computer information technology and is not discussed further herein.The information control loops can be configured to provide systemmanagement and optimized handover in several ways. Three such ways areshown by way of FIGS. 9 through 11. While the sequences of operationswithin the system may vary from those shown in FIGS. 9 through 11, suchsequences are numbered items (i.e., C1, C2, C3, . . . etc) for purposesof illustrative clarity indicating communications channels orconnections.

FIG. 9 is a relatively detailed diagram of one embodiment of themanagement system in accordance with the present invention with anon-board management system for a bus with an on-board route optimizationmechanism. In this exemplary embodiment of the invention, the system issupplied with starting parameters (at C1) such as the bus identificationand planned route. This information could be a manual input from the busdriver, from the network, or be derived from other bus hardware such aselectronic route signs. This information is used to determine whichroute map to use and select which data in stored RF switching locationtables should (at C2) be applied (at C4 and C5) to that route.

Ongoing location and relative-location information is determined using(at C3) technologies such as GPS, cell phone network Assisted GPS(AGPS), wireless transit beacons, the busses odometer and time. WhereGPS inaccuracies are significant, relative movement knowledge determinedby the bus's odometer can be used to give an improved accuracy. This isdone by tracing along the route from known accurate locations (such asareas where GPS is known to have good coverage) or from known featuresthat can be detected in the location information (such as turningcorners or stops at known bus stops). The time to instruct the radio tochange cell association can be determined from when the bus approachesthe pre-determined tabled radio change locations on the route. Thechange times may be further refined by taking into account the bussestravel speed and the exact lane it is traveling in. When the cellswitching time is reached, the radio is instructed to make the change.The identity of which cell to connect to next is already known from thetables (at C6, C7, C8, and C13) and the cell switching (at C9 and C10)can be done without searching the air for the best connection.

At all times, the cell radio receiver (at C11 and C12) can reportparametric information on the quality of the link. This can be used tofurther refine (at C14 and C15) the switching times and preventnon-optimum linking to cells that are delivering non-typicalperformance. This information can be logged and correlated against thebus's location on the route. The stored switching tables can be adjustedby analyzing signal strengths, connectivity durations, and achieved datarates in an iterative fashion for the next time the bus takes thatroute. Statistics from the bus and from the networked wireless equipmentcan be fed to a central management system for record keeping and futuresystem improvement work. Additionally, centrally known changes to routesdue to road works, weather conditions, equipment failures, and other busroute effecting parameters could be transmitted to the bus (at C16) andincluded in the switching table optimization.

FIG. 10 is a relatively detailed diagram of another embodiment of themanagement system in accordance with the present invention with anon-board management system for a bus with a centralized routeoptimization mechanism. The system shown in FIG. 10 is similar to thatshown in FIG. 9 except that the radio channel statistics, mapcorrelation to performance, and the switching tables optimization aremigrated to a centrally located system. This allows additionalinformation (at C17 and C18) to be included in the optimization such asnetwork equipment status and performance statistics, the effect ofloading from other buses and vehicles in the region where the bus is,and operational changes such as equipment under repair, route changesdue to road works, . . . etc. Route maps may also be updated by thissystem as required.

FIG. 11 is a relatively detailed diagram of yet another embodiment of amore centralized management system in accordance with the presentinvention with the primary on board management system that is normallyoverruled by a centralized management system while communications areworking. When communications or centralized systems fail the primaryon-board management system is capable of operating on its own. Routeoptimization is performed centrally.

The system shown in FIG. 11 is similar to that shown in FIG. 10 exceptthat a secondary control system located centrally has been added thatcalculates the best link and linking change times (at C17 a) usinginformation from the bus plus being able to make use of additionalcentrally based knowledge such as the latest information of road works,weather, network equipment status, other busses proximity and expectedpassenger loads (at C18). When communications with the bus are working,the secondary management system can override the on board system.However, when links fail the bus still has its own system that it usesto try and regain communications.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

1. A method of managing handover within a radio cellular environment,said method comprising: determining an identification of a mobilestation that is known to normally follow a predetermined routecorresponding to said identification; comparing said identification witha database having stored maps of known route segments including a listof base stations along each of said known route segments; and assigninga preferred sequence of base stations corresponding to one or more ofsaid known route segments along said predetermined route.
 2. The methodas claimed in claim 1, wherein said identification forms informationincluding ongoing location and relative-location information overabsolute time and relative time including one or more units of time. 3.The method as claimed in claim 2, wherein said information includes aunique route identifier.
 4. The method as claimed in claim 3, whereinsaid information further includes geographical location informationcorresponding to said mobile station.
 5. The method as claimed in claim4, wherein said information further includes time of day information. 6.The method as claimed in claim 5, wherein said information furtherincludes speed information corresponding to movement of said mobilestation.
 7. The method as claimed in claim 6, wherein said informationfurther includes directional information corresponding to directionalmovement of said mobile station.
 8. The method as claimed in claim 7,wherein said directional information is obtained from a directionalindication mechanism on board a vehicle upon which said mobile stationresides.
 9. The method as claimed in claim 8, wherein said methodfurther includes storing locally on board said vehicle said maps thatinclude said known route segments corresponding to said preferredsequence of base stations.
 10. The method as claimed in claim 9, whereinsaid database is centrally stored at a central server.
 11. A method ofoptimizing a managed handover technique within a radio cellularenvironment, said method comprising: determining an identification of amobile station traveling along a path, said mobile station having noprevious history of base station connectivity; as said mobile stationestablishes a connection with a base station, associating, based uponsaid base station being used by said mobile station, said identificationwith a known route selected from a database having stored maps of morethan one said known route including a list of base stations along eachsaid known route; as said mobile station disconnects from said basestation and connects to a subsequent base station, storing historicalinformation regarding said base station and said subsequent basestation; comparing said base station and said subsequent base station tosaid list of base stations along said known route in order to identifyone or more of said known routes that include both said base station andsaid subsequent base station; repeating said storing and comparing stepsfor further subsequent base stations, until only one of said knownroutes remains and corresponds to said path traveled by said mobilestation; determining whether a direction of travel of said mobilestation along said path is forward or reverse along said known routethat corresponds to said path; identifying one of said stored maps fromsaid database that correlates to both said direction of travel and saidknown route remaining that corresponds to said path traveled; andassigning a preferred sequence of base stations corresponding to saidone of said stored maps for all further connections with said mobilestation along said path.
 12. The method as claimed in claim 11, whereinsaid preferred sequence of base stations is derived from long termhistorical data for travel of said mobile station along one or more saidpath.
 13. The method as claimed in claim 11, wherein said preferredsequence of base stations is derived from an arbitrary visual inspectionof geographical maps that include available routes traveled by saidmobile station and available base stations.
 14. The method as claimed inclaim 11, wherein said preferred sequence of base stations is derivedfrom algorithms to calculate the optimized sequence.
 15. The method asclaimed in claim 14, wherein said preferred sequence of base stations isderived by a centralized database that tracks network throughput, eachbase station throughput, and each mobile station throughput whilemanaging base station connectivity to reduce data throughput congestion.16. A system for managing handover in a radio cellular environment, saidsystem comprising: a centralized communications center having a basetransceiver, a central server, and a database; a mobile station havingone or more transceivers capable of communication with said centralizedcommunications center via one or more base stations, said mobile stationbeing assigned a preferred sequence of said one or more base stationscorresponding to one or more known route segments along a predeterminedroute followed by said mobile station.
 17. The system as claimed inclaim 16, wherein said preferred sequence of said one or more basestations is selected from a plurality of possible sequences and saidplurality of possible sequences is stored in said database.
 18. Thesystem as claimed in claim 17, wherein said preferred sequence is storedwithin a memory of said mobile station.
 19. The system as claimed inclaim 18, wherein said mobile station further includes a locationdetection means for determining the location of said mobile station. 20.The system as claimed in claim 19, wherein said location detection meansis a global positioning device.
 21. A method of managing handover withina radio cellular environment, said method comprising: determining anidentification of a mobile station that is known to normally follow anindeterminate route corresponding to said identification; comparing saididentification with a database having stored maps of regions known toprovide optimum hard handover and regions known to provide optimum softhandover; and initiating the handover process when the mobile station iswithin said region.
 22. The method as claimed in claim 21, wherein saididentification forms information including ongoing continuous samples intime of absolute location.
 23. The method as claimed in claim 21,wherein said identification forms information including ongoingdiscontinuous samples in time of absolute location.
 24. The method asclaimed in claim 21, wherein said identification forms informationincluding ongoing continuous samples in time of relative location. 25.The method as claimed in claim 21, wherein said identification formsinformation including ongoing discontinuous samples in time of relativelocation.
 26. The method as claimed in claim 22, wherein the saididentification forms information regarding the direction of the mobilestation relative to the nearest handover region within the database mapof handover regions.
 27. A method of optimizing a location of handoverregions on a database map, said method comprising: utilizing pasthistorical data of previous base station radio links with mobilestations traveling pre-determined routes with associated information ofmobile station velocity; and selecting optimum handover regions for slowand fast velocities such that regions causing short durations ofhandovers are eliminated.
 28. The method of claim 27 wherein saidhandover region is specific to hard handover and soft handoverlocations.
 29. The method of claim 28 wherein said handover region forhard handover is defined as a boundary line and said regions are ageophysical location having geophysical location points.
 30. The methodof claim 28, wherein said handover region for soft handover is definedas an area enclosed by a boundary of geophysical location points.